GitLab

The client is notified of changes to the window owner.

BUG=756085,875111
TEST=covered by test

Change-Id: I8cec4fe2b547bb1f9f31899e2bc2a9437c186d27
Reviewed-on: https://chromium-review.googlesource.com/c/1343507
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611017}